1. Field of the Invention
The present invention concerns those fields involving the manufacture of electronic components, primarily the fabrication of integrated circuits from substrates or semiconductor wafer materials, such as silicon, more particularly the mechanical procedures and devices used to change the position of at least one semiconductor wafer provided with at least one positioning mark and placed in a support intended to hold a plurality of semiconductor wafers.
2. Discussion of Related Art
The prior art teaches that such methods consist primarily in grasping a semiconductor wafer by one of its faces to change its position, primarily by displacing it from one location to another, whereby devices used to implement these methods comprise means allowing a wafer to be grasped by suction in the central region of one of its faces. Independently of the displacement of the wafers from one location to another, the semiconductor wafers are oriented in such a way that their positioning mark is placed in a predetermined position, which operation may consist, for example, in aligning the positioning marks on all the wafers intended to be moved or situated in a common support.
The disadvantage of the methods and devices of the prior art is that they can lead to contamination of the semiconductor wafers resulting from the grasping of said wafers by one of their faces, which consists of a material that is highly sensitive to various forms of contamination, the risk of contamination being further enhanced by the fact that there is contact between the face and an object. Moreover, the methods and devices according to the prior art require considerable time for the operations of displacement and orientation of one or several semiconductor wafers, these operations being managed independently, which results in longer processing periods for semiconductor wafers and therefore higher processing costs.
We are familiar with document U.S. Pat. No. 5,102,291, which refers to a method and apparatus for orienting a silicon wafer located in a support by grasping its periphery so as to minimize possible contamination from direct contact with its faces. Wafers are grasped one by one between two gripper arms movable in translation with respect to one another along a straight line, which are urged toward each other in translation along the guide direction until the two arms exert pressure against the periphery of the wafer being grasped by means of four pressure wheels that lift the wafer prior to contact of the wheels against the periphery of the wafer, the grasped silicon wafer being capable of being rotationally oriented to a specific position with respect to the support by means of pressure wheels rotating in the plane of the wafer, at least one of which is motorized. Moreover, the apparatus is used to move the grasped wafer in a straight line only because of the two gripper arms. Detection of the desired orientation of the wafer can take place by means of a mechanical, optical, electrical, or other type of sensor. For wafers provided with a notch, the document specifies a pin that is smaller than the notch and which penetrates the notch when the wafer is in a desired position.
We are also familiar with U.S. Pat. No. 5,445,486, which relates to an apparatus for transferring silicon wafers from one support to another by means of a gripper arm inserted between wafers in a support, the gripper arm grasping one or more wafers by the periphery of their bottom surface. The apparatus does not have a means for orienting the transferred wafers.
The intended processing of semiconductor wafers can include any process involving a change in position of a wafer, of several wafers, or of all the semiconductor wafers located in a common support, as, for example, the transfer of wafers from one support to another, the alignment of marks for the purpose of identifying wafers in the support, or even modification of the angular position of the semiconductor wafer found in the support for the placement of marks at a predetermined position.
The present invention proposes to overcome the above disadvantages and provide other advantages. One object of the present invention is to enable the change of position of at least one semiconductor wafer while avoiding any contamination resulting from grasping the wafer by one of its faces and, furthermore, reducing the risks of contamination.
Another object of the present invention is to enable a change of position of at least one semiconductor wafer, thus modifying the orientation of a wafer while another processing operation is taking place, especially the displacement or transfer of the wafer.
Another object of the present invention is to provide increased space within a semiconductor wafer processing station by eliminating the need for specific equipment for the orientation or alignment of positioning marks on wafers.
Another object of the present invention is to enable a plurality of semiconductor wafers to be grasped and oriented, the orientation of the wafers occurring simultaneously and, moreover, simultaneously with another operation, such as the displacement of a plurality of wafers.